Siderail support arm



FIG. 1 is a perspective view of a siderail support arm;

FIG. 2 is a side elevation view of thereof;

FIG. 3 is another side elevation view thereof;

FIG. 4 is a side elevation view thereof;

FIG. 5 is another side elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines are for environmental purposes only and form no part of the claimed design. 

The ornamental design for a siderail support arm, as shown and described. 